Acute myocardial ischaemia induces cardiac carnitine release in man

In animal studies, prolonged periods of ischaemia decrease the cardiac carnitine content. However, whether in humans the heart loses carnitine during short-term ischaemia, and whether this is related to ischaemia-induced cardiac dysfunction, is as yet unknown. Carnitine kinetics were investigated in 28 normotensive patients with significant left coronary artery disease, during and after incremental atrial pacing. To evaluate carnitine kinetics from the ischaemic area, patients were grouped as those with (n = 22) or without (n = 6) myocardial lactate production. Atrial pacing resulted in a comparable maximal heart rate and ST depression in both groups. Carnitine kinetics did not change in those without lactate production. In contrast, coronary venous free carnitine levels increased significantly by 9% during pacing in those with lactate production. Cardiac free carnitine balance changed from uptake (255 +/- 107 pmol.min-1, mean +/- SEM) to release, (-150 +/- 66 pmol.min-1) at 30 min after pacing in the group with lactate production. Arterial and coronary venous differences in free carnitine were significantly correlated with myocardial lactate extraction immediately after pacing. The change in coronary venous free carnitine was significantly correlated with the change in left ventricular ejection fraction at 10 min after pacing. Thus, in patients with coronary artery disease, short-term mild myocardial ischaemia results in significant cardiac free carnitine loss.